Film-Tech Forum ARCHIVE: Soft Vertical Lines on Matte White Screen

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Posted by Adrian Hauser (Member # 4723) on 08-24-2011, 09:18 PM:

HI All,
We have just installed a new Matte White Screen (Harkness MW Super) in our theatre.
When projecting a white test pattern I can see soft vertical lines running in the screen. (They are not hard creases but soft 1" think looking lines. )The lines appear brighter than the projected white plane. I can only see a couple of these lines at any time and they only appear at the point of reflection between my position in the room and the projector.

The screen has been hanging now for two weeks.
The lines do not change when I zoom the lens on the projector or push the focus on the lens. THe lines do not dissappear when I remove the post glass.
Projector DP2kP.

Could it just be 'soft' fold marks in the screen. or could it be something line an "end of roll" screen? Or something else.

Thanks,
ADrian

Posted by Jerome Holmes (Member # 5013) on 08-24-2011, 10:35 PM:

This sounds like the seams for the screen. Each screen isn't really a solid piece, but composed of long strips fused together at their edges. I usually think its dimmer than other parts of the screen, but its possible that this area on your screen is devoid of perforations, resulting in more area to reflect light back (uneven with the distribution of perforations on the rest of the screen).

Posted by Adrian Hauser (Member # 4723) on 08-24-2011, 11:44 PM:

Thanks Jerome,

We have a non perf screen.

Looking at our 5m in width screen (screening room) I could say that these vertical 'soft' lines appear in groups of 2s. The are 2 lines are about 15 cm apart occurring every 70 cm.

The more I look at it it looks like a soft fold mark.

Adrian

Posted by Brian Guckian (Member # 1678) on 08-26-2011, 06:56 AM:

I'm just wondering if your surface has sagged very slightly. Is the tension OK?

Posted by Adrian Hauser (Member # 4723) on 08-29-2011, 03:37 AM:

Hi Brian,
We re-tensioned the screen last Friday. The lines are still there.

Hmmmm
Anyone?

Adrian

Posted by Frank Angel (Member # 248) on 08-29-2011, 05:37 AM:

Time to talk to Harkness & tell them of the problem. I thought Harkness was famous for NOT having visible seams. And if it is not seams, then whatever it is, they need to make it better. Also, when you say "soft folds," was this screen shipped folded? I thought Harkness shipped their screens on rolls.

If you have determined it is not the projector (zooming and changing focus) then it has to be the screen or some weird reflections from other light sources. I would turn every light in the hall off, including booth lights and see if you detect any light spill on the screen from any other source. Walk up close to the screen and see if you can created a shadow of any kind. Also, what is behind the screen? Any possibility that light hitting it from the rear could be causing this light pattern?

Posted by Alan Plester (Member # 852) on 08-29-2011, 05:43 AM:

Sounds like the screen joins to me, we had the same trouble with one of our screens for years, drives you mad, we changed eventually.

Posted by Frank Angel (Member # 248) on 08-29-2011, 07:08 AM:

I agree. But he's lucky; it's brand new. He should yell and scream to get Harkness to make good on their guarantee.

Posted by Brian Guckian (Member # 1678) on 08-29-2011, 08:15 AM:

Re. seams, note that Adrian reported that the lines are occurring every 70cm. Are seams that close together in this type of screen? I always thought they were spaced much further apart.

As Frank mentions, it would be good to know if the screen was shipped folded or rolled.

Posted by Phil Ranucci (Member # 3820) on 08-29-2011, 01:59 PM:

What's your screen frame made out of? We have one screen frame made on unisstrut that the installers didn't paint the joints so there is a reflection. Any chance the screen is being pushed out at the vertical braces?

Posted by Adrian Hauser (Member # 4723) on 09-02-2011, 05:37 PM:

I recall the screen arriving in a folded package. Definitely not a Rolled package.
I'll contact harkness.

I will also attempt to take a photo for reference.

Thanks,

ADrian Hauser

Posted by Adrian Hauser (Member # 4723) on 09-16-2011, 08:06 AM:

We have reordered a Matte Preview screen as a replacement.
It seems the problem was a manufacturing issue possibly from the calendering process.

Regards ,
Adrian